Lambdoidal ladder

ABSTRACT

A lambdoidal ladder comprises front struts ( 100 ), back struts ( 200 ), treads ( 500 ), a folding device) 400, a connection device ( 600 ) and a platform ( 300 ). Wherein the platform ( 300 ) is connected to the front strut ( 100 ) and the back strut ( 200 ), and the structure between the front strut and the back strut is a rotatable connection; the platform ( 300 ) comprises a body ( 310 ) and a transverse rod ( 320 ) which goes through the front strut ( 100 ), an orientation slot ( 314 ) matching to the transverse rod ( 320 ) is set under the body ( 310 ); the folding device ( 400 ) fixed to the middle part of the front strut and the back strut is constructed a hinge with a H figuration; the tread ( 500 ) is fixed to the front and back struts by the connection device ( 600 ).

FIELD OF THE INVENTION

The present invention relates to a lambdoidal ladder, more particularly,to a foldable lambdoidal ladder.

BACKGROUND OF THE INVENTION

The foldable lambdoidal ladder of the prior art comprises front struts,back struts, treads, a folding device and a platform. The platform is aplastic parts directly and pivotally connected to tops of the frontstruts and back struts, which make the structure between the front strutand the back strut be a rotatable connection. The platform of thelambdoidal is functioned as: 1, connecting the front struts with thebake struts, 2, be a platform in working. Because the plastic partsdirectly and pivotally connected to the front struts and the backstruts, thus it has the following drawbacks: firstly, the connectionstrength is not strong enough to be a working platform; secondly, theplastic parts pivotally connected both to the front struts and the backstruts, which is not convenient in assembly.

And the connection structure between the struts and the treads of thelambdoidal ladder generally have the following two forms: the first oneis to lock the strut and the tread by a locking element directly; thesecond one is to set through holes in the strut, then the ends of thetreads inserted into the holes to be locked. The first connectionstructure has the following drawbacks: firstly, the cut force generatedbetween the tread and the strut is forced entirely on the lockingelement, therefore the locking member is easy to be broken, and hasshort use time and lower use safety; secondly, the tread of the priorart generally is hollow structure, therefore, the locking member mustlocked inside the hollow tread, this is not convenient in locking orassembly; thirdly, the tread may be rotated in use thus the use safetyis not enough. The second connecting structure has the followingdrawbacks: firstly, through holes are set in the struts, thus lower thestrength of the struts, if the strength is to be enhanced, it must addthe sectional area of the struts or use solid structure, which will addthe amount of the material and add the cost of production; secondly, thestructure of the treads of the prior art are mostly hollow, the lockingmember is locked inside the hollow tread, thus both the locking and theassembly are not convenient.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a lambdoidalladder which obviates the disadvantage of the lambdoidal ladder of theprior art that the platform is not strong enough in connection and isnot strong enough as a working platform.

Another object of the present invention is to provide a lambdoidalladder which obviates disadvantage of the lambdoidal ladder of the priorart that the treads are not strong enough in connection.

A further object of the present invention is to provide a lambdoidalladder which obviates disadvantage of the lambdoidal ladder of the priorart that the folding device is not strong enough.

Solution 1

A lambdoidal ladder comprises front struts, back struts, treads, afolding device, a connection device and a platform; the platform isconnected to the front strut and the back strut, and the structurebetween the front strut and the back strut is a rotatable connection;the platform comprises a body and a transverse rod which goes throughthe front strut, an orientation slot matching to the transverse rod isset under the body; wherein said body is connected to said front struts,and the orientation slot of the body is supported on the transverse rod;the folding device fixed to the middle part of the front strut and theback strut is constructed a hinge with a H figuration; the tread isfixed to the front and back struts by the connection device.

A plurality of reinforcement ribs which arranged spaced and parallel areformed under said body, grooves matching with said transverse rod areupwardly formed under said reinforcement ribs, said grooves are arrangedlengthwise so as to form the orientation grooves matching to thetransverse rod.

Or a lengthwise orientation bar and a plurality of reinforcement ribswhich arranged spaced and parallel are formed under said body, saidorientation bar is crossly connected with said reinforcement ribs, and aorientation groove matching to the transverse rod is set under theorientation bar.

The edge of said body is extended downwardly to form a periphery, hereinsaid body connected to said front struts, said periphery sleeved on thetop ends of said struts, and the transverse rod is gone through saidfront struts and connected to said periphery.

Said H-shaped hinge comprises a transverse rod, a pair of front verticalrods and a pair of rear vertical rods; said rear vertical rods areU-shaped rods, the rear ends of said front vertical rods are insertedinto said rear vertical rods; the front ends of said front vertical rodsare fixed to the outside of the two front struts; the rear ends of tworear vertical rods are fixed to the outside of the two rear struts; thevertical rod is fixed between the two front vertical rods.

Said connection device comprises: a connection element, the outside ofsaid connection element is sleeved to the top end of said tread, theinner side of said connection element is connected to the struts and islocked to said connection element by a locking element passing throughthe strut.

Said connection element comprises a middle piece, an insertion portionand a protrusion portion, said insertion portion and said protrusionportion are respectively fixed to the front and rear of said middlepiece, herein the insertion portion is matching to and inserted to theinner side of said hollow strut; a lengthwise groove is disposed in thestrut, said lengthwise groove is fixedly connected to the protrusion ofsaid connection element.

Said connection element is an integrated structure, the front side ofsaid middle piece is fixed to the rear side of said insertion portion,said middle piece is provided with a front protrusion which is extendedout said insertion portion; herein said insertion portion is insertedinto the inner side of said hollow strut, said front extending side isabut against the opening of said hollow tread.

The back side of said middle piece is fixed with said protrusionportion, said middle piece is provided with a back extending side whichis extended out said protrusion portion; herein said protrusion portionis inserted into the lengthwise groove of said strut, said backextending side is abut against said strut, said protrusion is matchingto the bar-shaped protrusion of said lengthwise groove.

Another Solution

The front side of said connection element is provided with a orientationgroove, the inner edge of said connection element is matching to theouter edge of the section of said tread, the end portion of said treadis positioned and supported inside said orientation groove, saidconnection element is fixed to the strut.

Said connection element comprises a base and two protrusionsrespectively disposed to the left side and right side of said base, saidorientation groove is positioned on said base, said two protrusions areextended to the rear of said base, herein the rear side of said base isfixed and abut against to the first side of the strut, said twoprotrusions are respectively abut against two second sides which arenext to the first side of the strut.

The abut connection between said protrusion and strut is a tight abutconnection.

The first side of said strut is concaved to form a middle groove, saidbase is protruded backwardly to form a middle element, said middleelement is disposed inside of said middle element and they are tightfit.

Compared with the prior art, because the platform comprises a body and atransverse rod, the body is supported by the transverse rod, thus theplatform is strong itself, because the transverse rod is connected tofront strut, the platform is connected to the front strut via thetransverse rod, thus the connection between the platform and the frontstrut is strong Because the body is provided with orientation groove,the orientation groove is supported on the transverse rod, thus theorientation is accuracy, and the stability and fastness of the supportis high. Because the body is formed with reinforcement ribs, thus isfacilitate to be manufactured to increase the intension. Because thereinforcement ribs are provided with groove, thus the support betweenthe transverse rod and the body has accurate orientation. Because thereinforcement ribs are provided with orientation bars below, and theorientation bars are provided with grooves, thus the strength of thebody can be reinforced, and the support between the transverse rod andbody are reinforced also. Because the periphery is sleeved to the topends of the front struts, thus the appearance is well. The transverserod is pass through the front strut and connected to the periphery, theconnection is stable, reliable and with high support reliability.Because the rear strut is inside the periphery, thus the appearance iswell. Because the orientation bar is fixed to the periphery, thus can beintegrated-formed, the connection is with high strength. Moreover,because the tread is connected to the pipe of the strut via theconnection element, the outside of the connection element is fixed tothe leg pipe, the inner side is sleeved to the end portion of the tread,thus the leg pipe can be without any through holes, and the end portionof hollow tread is sleeved to the connection element, which add thecontacting area to the leg pipe, the strength is enhanced. On the otherhand, because the folding device is adapted to be H-shaped hinge, thefolding and unfolding are more convenient, and is more stable in use.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings contain figures of preferred embodiments tofurther clarify the above and other aspects, advantages and features ofthe present invention. It will be appreciated that these drawings depictonly preferred embodiments of the invention and are not intended tolimits its scope. The invention will be described and explained withadditional specificity and detail through the use of the accompanyingdrawings in which:

FIG. 1 is a perspective view of the embodiment 1 of the presentinvention.

FIG. 2 is an exploded view of the embodiment 1 of the present invention.

FIG. 3 is a bottom perspective view of the embodiment 1 of the presentinvention.

FIG. 4 is a perspective view of the platform in the embodiment 1 of thepresent invention.

FIG. 5 is a front view of the hinge in the embodiment 1 of the presentinvention.

FIG. 6 is a perspective view of the hinge in the embodiment 1 of thepresent invention.

FIG. 7 illustrates the connection portion of the tread in embodiment 1of the present invention.

FIG. 8 is a partial enlarged view of FIG. 7

FIG. 9 is a sectional view of the tread in embodiment 1 of the presentinvention.

FIG. 10 is a sectional view of the tread in embodiment 2 of the presentinvention.

FIG. 11 is a sectional view of the tread in embodiment 3 of the presentinvention.

FIG. 12 is a perspective view of the embodiment 4 of the presentinvention.

FIG. 13 is a partial enlarged perspective and exploded view of theembodiment 4 of the present invention.

FIG. 14 is a perspective view of the connection element in theembodiment 4 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1, Referring to FIG. 1 to FIG. 9, a lambdoidal laddercomprises front struts 100, back struts 200, a platform 300, a hinge400, treads 500, and connection devices 600.

The treads 500 are disposed between the two front struts 100 via theconnection devices 600; back transverse rods or treads 500 are spaceddisposed between the two back struts 200; the platform 300 is disposedon the tops of the front strut 100 and the back strut 200; the hinge 400is H-shaped and is disposed between middles of the front strut 100 andthe back strut 200.

Referring to FIG. 1 to FIG. 4, the platform comprises a body 310 and atransverse rod 320. The edges of the body 310 extended downwardly toform a periphery 311. The bottom of the body 310 is formed with aplurality of spaced and parallel transversely reinforcement ribs 312 anda plurality of spaced and parallel lengthwise reinforcement ribs 313,both the reinforcement ribs 312 and 313 are fixedly connected to theperiphery 311. Each transverse rib 312 is provided with a groove 314opened upwardly, these grooves 314 are arranged lengthwise to form aorientation groove for matching to the transverse rod 320, and theposition of the orientation groove is towards to one of the lengthwiseribs 313. The sectional shape of the transverse rod 320 is round, orother shape such as rectangle or hexagon etc.

The body 310 of the platform 300 is connected to the front struts 100,the periphery 311 is sleeved to the top end of the struts 100; thetransverse rod 320 transversely pass through the two front rods of thefront struts 100. The transverse rod 320 is supported in the orientationgroove of the body, and the end portion of the transverse rod 320,extended out the front struts 100, is inserted to the periphery 311 soas to form a fixation connection structure between the platform 300 andthe front struts 100.

The back struts 200 are pivotally connected to the bottom of the body310 and are within the periphery 311 so as to form a rotation connectionbetween the front struts 100 and the back struts 200.

Hinge 400: referring to FIG. 5 and FIG. 6, the hinge 400 used as afolding device is H-shaped, which comprises a transverse rod 410, a pairof front lengthways rods 420 and a pair of back lengthways rods 430; theback lengthways rods 430 are U-shaped rods, and the back end of thefront lengthways rods 420 are respectively inserted between the backlengthways rods 430; the front ends of the front lengthways rods 420 arefixed to the outside of the two front struts 100; the back ends of thefront lengthways rods 430 are fixed to the outside of the two backstruts 200; the transverse rod 410 is fixed between the two frontlengthways rods 410, and the outside of the front lengthways rods 420are respectively formed orientation protrusions 421, moreover, thetransverse rod 410 is provided with a handle portion 411 in the middle.The hinge 400 is used to let the lambdoidal ladder to be in a stableunfolded status. In folding of the lambdoidal ladder, draw downwardly ofthe handle portion 411, let the back ends of the front lengthways rods420 free from the back lengthways rods 430, the front rods 420 and theback rods 430 rotated relative to each other until the protrusion 421 ofthe outside of the front lengthways rods 420 are abut against the backlengthways rods 430. And drive the back struts 200 to rotate relative tothe platform 300 to near to the front struts 100.

Treads 500: referring to FIG. 7 and FIG. 9, each hollow tread 500comprises a body 510 which has a triangle section comprising a top boardand two lower boards. An axial clamping reinforcement opening 520 isdisposed in the middle of the bottom of the body 510, and an axialreinforcement clamping opening 530 is disposed in the angle of the twolower boards, an reinforcement piece 540 is disposed between the tworeinforcement opening 520, 530, thus the inner hole of the hollow tread500 is separated into two parts by the reinforcement piece 540. Detailedstructure of the treads 500 can be seen in the prior patent of thepresent inventor in ZL200520126388.6.

Connection device 600: referring to FIG. 7 and FIG. 8, the connectiondevice 600 comprises a connection element 610, a lengthways groove 620,a gasket 630 and a locking element 640. The lengthways groove 620 isaxially disposed in the inner side of the front strut 100.

The connection element 610 comprises a middle piece 611, an insertionportion 612 and a protrusion 613, which are made by one-piece-processingtechnology. The back side of the insertion portion 612 is fixed to thefront side of the middle piece 611, the structure of the insertionportion 612 comprising two separated portions is matching to the shapeof the inner hole of the hollow tread 500. The front portion of theprotrusion portion 613 is fixed to the back side of the middle piece611, the protrusion 613 is a bar-shaped protrusion matching with thelengthways groove 612. Herein the middle piece 611 comprises a frontextending side extended out the insertion portion 612 and a backextending side extended out the protrusion 613.

The insertion portion 612 of the connection element 610 is inserted intothe inner hole of the hollow treads 500 (the two independent portionsrespectively inserted into the two corresponding portions of the innerhole), the protrusion 613 of the connecting element 610 fixedly insertedinto the lengthways groove 620, and the front extending side of themiddle piece 611 is abut against the end of the hollow tread 500, theback extending side is abut against the front strut 100. Because theinner part of the hollow tread 500 is separated into two parts, thus theinsertion portion and the hollow tread can not be rotated relative toeach other. According to requirement, the connection between theprotrusion 613 and the lengthways groove 620 is interference fit.

The gasket 630 is abut against the outside of the front strut 100. Thelocking element comprises two tapping screws arranged up and down, andthe locking end of the tapping screw is pass through the gasket 630, thefront strut 100, the lengthways groove 620 and the protrusion 610 of theconnecting element 610 in turn, then inserted into the reinforcementopening. Herein the friction force between the gasket and the frontstrut can bear part of the shearing force so as to protect the strut.

Embodiment 2, referring to FIG. 10, the difference of this embodiment toembodiment 1 is that: the hollow tread 500 comprises a body 510 and areinforcement board 520, the body 510 is a shape similar to a rectanglecomprising an upper board and a lower board, the reinforcement board 540is connected between the upper board and the lower board of the body510.

Embodiment 3, referring to FIG. 11, the difference of this embodiment toembodiment 2 is that: the hollow tread 500 comprises a body 510, thebody 510 is a shape similar to a rectangle comprising an upper board anda lower board, two axial reinforcement openings 520 and 530 arerespectively disposed in the middles of bottom side of the upper boardand the upper side of the lower board.

Embodiment 4, Referring to FIGS. 12, 13 and 14, the difference of thisembodiment to embodiment 1 is that the connection device between thetread 500 and the front strut 100 is different.

Connection device 700: comprises a connection element 760, areinforcement gasket 770 and a locking bolt 780. The connection element760 comprises a base 761 with a cross shape, two protrusions 762respectively disposed on the left side and right side and extendedbackwardly, and two middle portions 763 respectively fixed the up andlower portions of the base 761 and extended out the base 761. The base761 has a orientation groove 764 which opened forwardly, the shape ofthe section of the orientation groove 764 is matching with the shape ofthe end of the tread 500.

Referring to FIG. 9 and FIG. 12, the end portion of the tread 500 ispositioned in the groove 764 of the connection element 760. The backside of the base 761 is abut against and fixed to the first side of thefront strut 100 via the reinforcement gasket 770, the two protrusions762 respectively abut against the two second sides (left and rightsides) near to the first side of the front strut 100, the middle element763 is inside the middle groove 64 and form a tight fit. Thereinforcement 770 is positioned in the middle groove 64 and fixedbetween the connection element 760 and the front strut 100. Bolts 780pass through the front strut 100 and the connection element 760 andinserted into the opening 520 of the tread 500 by the bolting end.

The invention also can be a single-side lambdoidal ladder. i.e. treadsare disposed between the two front struts, and supporting rods aredisposed between the two back struts; or two-side lambdoidal ladder,i.e. treads are disposed both between the two front struts and the twoback struts.

INDUSTRIAL APPLICABILITY

The lambdoidal ladder of the present invention comprises front struts,back struts, treads, a folding device, a connection device and aplatform. the platform comprises a body and a transverse rod which goesthrough the front strut, an orientation slot matching to the transverserod is set under the body; the folding device fixed to the middle partof the front strut and the back strut is constructed a hinge with a Hfiguration; the tread is fixed to the front and back struts by theconnection device. the invention has simple structure, well workingeffect and high strength.

1. A lambdoidal ladder comprises front struts, back struts, treads, afolding device, a connection device and a platform; the platform isconnected to the front strut and the back strut, and the structurebetween the front strut and the back strut is a rotatable connection;the platform comprises a body and a transverse rod which goes throughthe front strut, an orientation slot matching to the transverse rod isset under the body; wherein said body is connected to said front struts,and the orientation slot of the body is supported on the transverse rod;the folding device fixed to the middle part of the front strut and theback strut is constructed a hinge with a H figuration; the tread isfixed to the front and back struts by the connection device.
 2. Thelambdoidal ladder according to claim 1, wherein a plurality ofreinforcement ribs which arranged spaced and parallel are formed undersaid body, grooves matching with said transverse rod are upwardly formedunder said reinforcement ribs, said grooves are arranged lengthwise soas to form the orientation grooves matching to the transverse rod. 3.The lambdoidal ladder according to claim 1, wherein a lengthwiseorientation bar and a plurality of reinforcement ribs which arrangedspaced and parallel are formed under said body, said orientation bar iscrossly connected with said reinforcement ribs, and a orientation groovematching to the transverse rod is set under the orientation bar.
 4. Thelambdoidal ladder according to claim 2, wherein the edge of said body isextended downwardly to form a periphery, wherein said body connected tosaid front struts, said periphery sleeved on the top ends of saidstruts, and the transverse rod is gone through said front struts andconnected to said periphery.
 5. The lambdoidal ladder according to claim1, wherein said H-shaped hinge comprises a transverse rod, a pair offront vertical rods and a pair of rear vertical rods; said rear verticalrods are U-shaped rods, the rear ends of said front vertical rods areinserted into said rear vertical rods; the front ends of said frontvertical rods are fixed to the outside of the two front struts; the rearends of two rear vertical rods are fixed to the outside of the two rearstruts; the vertical rod is fixed between the two front vertical rods.6. The lambdoidal ladder according to claim 1, wherein said connectiondevice comprises: a connection element, the outside of said connectionelement is sleeved to the top end of said tread, the inner side of saidconnection element is connected to the struts and is locked to saidconnection element by a locking element passing through the strut. 7.The lambdoidal ladder according to claim 6, wherein said connectionelement comprises a middle piece, an insertion portion and a protrusionportion, said insertion portion and said protrusion portion arerespectively fixed to the front and rear of said middle piece, hereinthe insertion portion is matching to and inserted to the inner side ofsaid hollow strut; a lengthwise groove is disposed in the strut, saidlengthwise groove is fixedly connected to the protrusion of saidconnection element.
 8. The lambdoidal ladder according to claim 7,wherein said connection element is an integrated structure, the frontside of said middle piece is fixed to the rear side of said insertionportion, said middle piece is provided with a front protrusion which isextended out said insertion portion; herein said insertion portion isinserted into the inner side of said hollow strut, said front extendingside is abut against the opening of said hollow tread.
 9. The lambdoidalladder according to claim 7, wherein the back side of said middle pieceis fixed with said protrusion portion, said middle piece is providedwith a back extending side which is extended out said protrusionportion; herein said protrusion portion is inserted into the lengthwisegroove of said strut, said back extending side is abut against saidstrut, said protrusion is matching to the bar-shaped protrusion of saidlengthwise groove.
 10. The lambdoidal ladder according to claim 6,wherein the front side of said connection element is provided with aorientation groove, the inner edge of said connection element ismatching to the outer edge of the section of said tread, the end portionof said tread is positioned and supported inside said orientationgroove, said connection element is fixed to the strut.
 11. Thelambdoidal ladder according to claim 10, wherein said connection elementcomprises a base and two protrusions respectively disposed to the leftside and right side of said base, said orientation groove is positionedon said base, said two protrusions are extended to the rear of saidbase, herein the rear side of said base is fixed and abut against to thefirst side of the strut, said two protrusions are respectively abutagainst two second sides which are next to the first side of the strut.12. The lambdoidal ladder according to claim 10, wherein the abutconnection between said protrusion and strut is a tight abut connection.13. The lambdoidal ladder according to claim 10, wherein the first sideof said strut is concaved to form a middle groove, said base isprotruded backwardly to form a middle element, said middle element isdisposed inside of said middle element and they are tight fit.
 14. Thelambdoidal ladder according to claim 7, wherein treads are disposedbetween the two front struts, or treads are disposed both between thetwo front struts and the two back struts.
 15. The lambdoidal ladderaccording to claim 3, wherein the edge of said body is extendeddownwardly to form a periphery, wherein said body connected to saidfront struts, said periphery sleeved on the top ends of said struts, andthe transverse rod is gone through said front struts and connected tosaid periphery.
 16. The lambdoidal ladder according to claim 10, whereintreads are disposed between the two front struts, or treads are disposedboth between the two front struts and the two back struts.